Well, now I've heard them all - "Only last 3 or 4 months".
Find a large stationery shop that sells custom rubber stamps, get one made with the word "IDIOT" in 2" capital letters, then stamp it across that guy's forehead with red insoluble ink.
I have never heard so much guff in my life. Symetrical tyre wear indicates either over pressure (centre tyre wear - does she skid/spin wheels?) or under pressure (both edges wear).
The amount of wear you describe on Dunlops would be the equivalent of a good year's (sorry) enthusiastic driving, so there is something other than tracking that is wrong. Tracking faults would feather the shoulders of the tyres and give poor, indistinct steering.
Either that or she's far too enthusiastic and does dougnuts without telling you